Aromatic hydrocarbons find a plurality of uses in various chemical synthesis industries. In one non-limiting example, para-xylene is an important intermediate aromatic that finds wide and varied application in chemical syntheses. Upon oxidation, para-xylene yields terephthalic acid. Polyester fabrics and resins are produced from a polymer of ethylene glycol and terephthalic acid. These polyester materials are used extensively in a number of industries and are used to manufacture such items as, for example, clothing, beverage containers, electronic components, and insulating materials.
In prior art processes, C9 aromatic hydrocarbons are separated from C8 aromatic hydrocarbons, for example xylene isomers, by fractional distillation. This requires heating of the admixture to vaporize the C8 and lighter aromatic hydrocarbons. A large portion of the isomerization stream must be vaporized to accomplish the C9 separation because the stream is generally composed primarily of C8 and lighter aromatic hydrocarbons. After the C9 aromatic removal, the C8-containing stream is then recycled into an adsorptive separation unit. Multiple, large fractionation columns are often required to accomplish these process steps. As such, this separation process requires a substantial amount of energy and associated capital costs.
The production of aromatic hydrocarbon isomers, including for example para-xylene, is practiced commercially in large-scale facilities and is highly competitive. A never-ending drive exists to decrease the energy costs and capital costs yet increase the effectiveness associated with the conversion of a feedstock through one or more of isomerization, transalkylation, and disproportionation to produce select isomers and separate the select isomers from the resultant mixture of C8 aromatic isomers.
Accordingly, it is desirable to provide processes for the production of particular aromatic isomers, including the separation of such isomers from an admixture of C8 and C9 aromatic isomers, that lowers operational expenses, particularly energy consumption. In addition it is desirable to provide processes for the production of particular aromatic isomers that lowers capital expenditures, in the form of processing equipment and the size of such processing equipment. Further, it is desirable to provide split-shell fractionation columns for use in such processes. These and other desirable features and characteristics will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.